1. Field of the Invention
The present invention relates to a technique to reduce a load accompanying the change of specifications of a semiconductor memory.
2. Description of the Background Art
In nonvolatile semiconductor memories in which game data and the like are stored, commands are inputted from external systems and various operations, such as reading of data from desired addresses, deletion of desired blocks, writing of data into desired pages or the like, are performed in response to the commands.
(Patent Document 1) Japanese Patent Application Laid Open Gazette No. 2001-283170.
Taking, e.g., game cassettes used for game devices as an example of semiconductor memories, commands encrypted in the system are generally used in order to prevent an illegal copy of game software. But if the encrypted commands are decoded, the specifications of the semiconductor memory have to be changed as soon as possible.
In the conventional semiconductor memories, however, combinations of the commands and operations are fixed to each of the semiconductor memories and if the commands are changed or added, redesign of the whole semiconductor memory is disadvantageously needed.
Further, if the specifications of the semiconductor memory is changed, the external system (e.g., a game device or the like) using it has to respond to the change, and this requires more costs. Furthermore, if the external system is a game device or the like, it is preferable that the specifications should not be changed for relatively long time in order to ensure compatibility.